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A simple model for the size and shape dependent Curie temperature of freestanding Ni and Fe nanoparticles based on the average coordination number and atomic cohesive energy
, Article Chemical Physics ; Volume 383, Issue 1-3 , 2011 , Pages 1-5 ; 03010104 (ISSN) ; Madaah Hosseini, H ; Simchi, A ; Sharif University of Technology
Abstract
To study the effect of size and shape of metallic nanoparticle on their Curie temperature, an analytical model is proposed. The core average coordination number (CAC) and surface average coordination number (SAC) of freestanding nanoparticles are considered in the model. Clusters of icosahedral (IC) and body centred cubic (BCC) structure without any vacancies and defects are modelled. A critical Curie temperature is introduced for metallic clusters with a diameter of 2-3 nm. This critical diameter is related to clusters which the ratio of surface atoms to total atoms is about 50%. The "shape effect" is shown to be important at sizes less than 20 nm. The obtained results are supported by...
Design and Synthesis of Ni-Zn Magnetic Nanoparticles for Hyperthermia Treatment
, Ph.D. Dissertation Sharif University of Technology ; Madaah Hosseini, Hamid Reza (Supervisor) ; Simchi, Abdolreza (Supervisor)
Abstract
Hyperthermia (also called thermal therapy or thermotherapy) is defined as a type of cancer treatment in which body tissue is exposed to high temperatures, to damage and kill cancer cells, or to make cancer cells more sensitive to the effects of radiation and certain anticancer drugs. The temperature increase required by hyperthermia can be achieved via different heat sources, such as electromagnetic radiation waves (radiofrequency or microwave, ultrasound waves and electrical current. These techniques have shown good results, however, the major problem with present conventional methods is reaching homogenous heat distribution and therapeutic temperatures in the deep region of the tumor to be...
Melting enthalpy and entropy of freestanding metallic nanoparticles based on cohesive energy and average coordination number
, Article Journal of Physical Chemistry C ; Volume 115, Issue 35 , August , 2011 , Pages 17310-17313 ; 19327447 (ISSN) ; Delavari H., H ; Madaah Hosseini, H. R ; Sharif University of Technology
2011
Abstract
An analytical model is proposed to study the effect of particle size on melting enthalpy and entropy of metallic nanoparticles (NPs). The Mott's and Regel's equations for melting entropy in the combination of core average coordination number (CAC) and surface average coordination number (SAC) of freestanding NPs are considered. Clusters of icosahedral (IC), body centered cubic (BCC), and body centered tetragonal (BCT) structure without any vacancies and defects are modeled. Using the variable coordination number made this model to be in good agreement with experimental and molecular dynamic (MD) results of different crystal structures. The model predicts melting entropy and enthalpy of...
Effects of particle size, shape and crystal structure on the formation energy of Schottky vacancies in free-standing metal nanoparticles: A model study
, Article Physica B: Condensed Matter ; Volume 406, Issue 20 , October , 2011 , Pages 3777-3780 ; 09214526 (ISSN) ; Madaah Hosseini, H. R ; Simchi, A ; Sharif University of Technology
2011
Abstract
A simplified model based on cohesive energy is proposed to estimate the formation energy of Schottky vacancies (VFE) in free-standing metal nanoparticles with BCC and FCC crystal structures. To study the effect of particle size and shape, the surface energy, elastic contraction and average coordination number of particles at the surface and core was considered. It is shown that the energy of vacancy formation in FCC nanoparticles increases with decreasing the size while the effect of particle shape (sphere, cubic and icosahedral) is marginal. In spite of this behavior, BCC nanoparticles exhibit a critical particle size at around 25 Å, at which a minimum VFE is attained. Additionally, the...
Estimation of carbonates permeability using pore network parameters extracted from thin section images and comparison with experimental data
, Article Journal of Natural Gas Science and Engineering ; Volume 42 , 2017 , Pages 85-98 ; 18755100 (ISSN) ; Assadi, A ; Kharrat, R ; Dashti, N ; Ayatollahi, S ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Petrography and image analysis have been widely used to identify and quantify porous characteristics in carbonate reservoirs. This paper uses the thin section images of 200 carbonate rock samples to predict the absolute permeability using intelligent and empirical methods. For each thin section, several pore network parameters are extracted from thin section images of rocks including the average pore size, average throat size, average throat length and average 2-D coordination number of pore network. A neural-based model successfully predicts the permeability of samples using pore network parameters as the inputs. Second neural network is applied for predicting absolute permeability...
A rigorous algebraic-analytical method for pore network extraction from micro-tomography images
, Article Journal of Hydrology ; Volume 590 , 2020 ; Masihi, M ; Azadi Tabar, M ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Static and dynamic properties of porous media are highly dependent on its internal geometry. CT scan images are generally used to characterize porous media geometry. Direct simulation of fluid flow on CT scan images is possible but considerably time-consuming. In this study, a new method was developed for extracting a simplified representation known as “pore network model” by utilizing a rigorous algebraic-analytical method. By using a moving frame in the 3D matrix of the CT scan image and stepwise identifying-removing of image components, running time for a 4003 voxels sample in a typical computer system decreased to less than 350 s. The identification of throats was based on a new...